This invention relates to a method of controlling or removing zebra mussels from surfaces of waterways, surfaces of facilities in waterways, such as watercraft, docks, marinas and the like, and from the ballast water of watercraft, and more particularly to a method of killing the zebra mussels in such water and on water contacting surfaces of such facilities by isolating the surfaces of the facilities in a batch of water and heating the water to a sufficient temperature for a sufficient time.
Dreissena Polymorpha, commonly known as zebra mussels, were unknown in the waters of the United States and Canada prior to 1988. They are indigenous to Europe and it is theorized that these prolific breeders entered the waters of Lake St. Clair when a foreign ship emptied its ballast water. Since then zebra mussels have found their way into the Great Lakes, namely Lake Erie and Lake Ontario and have already been reported in the Ohio and Tennessee river systems. A single female zebra mussel may lay some ten thousand to two million eggs per year which have a four to eight year life cycle comprising four stages: the fertilized egg stage lasting some two to three days, the veliger or larvae stage lasting some two to three weeks, the settling stage and the adult stage which begins at about twelve months. In the veliger stage the zebra mussels are a free swimming planktonic larval which may disperse for miles. It is in this stage that they are small enough to enter through the screens of a power plant such as an electrical utility generating plant and municipal and industrial water plants drawing their water supply from the contaminated rivers and lakes. In the settling stage they are visible to the eye and possess visceral threads, known as byssus, which cling to or attach to almost any solid stationary surface in areas having low velocity currents, e.g. less than approximately seven feet per second. In this stage they attempt to attach or connect onto such surfaces and if a clear surface is not available, they will climb on top of others that are so attached. In this manner they colonize on the condensers and other equipment on such plants, on the bottoms of watercraft, on docks and pilings, in the ballast of vessels, and on the bottoms of waterways, and may form into mats or clumps up to five inches thick. The zebra mussels have few natural predators and can stay out of water for substantial periods of time, up to 14 days, merely needing moist or humid areas in which to exist.
A solution to the problem of controlling zebra mussels in electric utility power plants and water plants was proposed in our aforesaid copending patent application by isolating the water in the inlet cell of such plants prior to its entering the distribution lines within the plant, the water being held in the inlet cell and heated to a lethal temperature which is maintained for a sufficient time to assure 100 percent mortality to the zebra mussels in any of its life cycle stages. However, problems remain with regard to zebra mussels within waterways, and on watercraft and on facilities and equipment along the waterways.